This is in reference to http://dev.w3.org/2006/webapi/selectors-api/ as it
stands today.
In section 2, the text
If an exception is raised by the NSResolver while resolving
namespaces, processing must be aborted and the exception
propagated to the caller.
has the "must" in lowercase and red text, whereas all other MUSTs I see are
uppercase and a different font from the rest of the text.
-Boris